https://minecraft-statistic.net is a site that collects information on specific minecraft servers and users that play on those servers. It does NOT include all minecraft servers, only those it counts as “popular”. 9 out of 10 times you may not get a result here, but if you are suspicious that there is something up with the applicant then its worth checking.
When you search a name, you are given a list of people who have used that name, and the servers they may have played on, their current skin, and also players that the user may have interacted with. This information is gathered from servers that players have in common.
The helpful part of this site is that might give you information about a players known associates. This is useful when you think someone might be part of a group of players that is causing issues, or when a few players from one server join and cause issues. You can check to see if a new whitelist is associated with that server or players.
Here’s the profile of a random minecraft user (chosen randomly from the minecraft-statistics site).
You can see the servers they have previously played on, and even the one they are currently playing.
Scrolling down you can see the list of players that may have played on the same servers. People that this user may (or may not) know.
It sounds like a stretch, but we have once or twice found people who have caused issues to be associated with other people who have caused issues via this site. So it can be useful on occasion.